Fire-climate-vegetation-topography-land use

1. Fire-climate-vegetation-topography-land use What drives and determines fire patterns across time and space? What are the implications of global climate change?

2. Global climate change • Avg. surface T increased by 0.6C in 20th century • 1990s were warmest decade and 1998 was warmest year since 1861, and probably the warmest of the last 1000 yr • Freeze-free season longer in mid and high latitudes • Less snow and ice, higher sea levels

3. Global temperatures • Mean global temperatures in 2000 were 0.39C (0.7F) above the long-term (1880-1999) average • 2000 was the sixth warmest year on record • The only years warmer were 1998, 1997, 1995, 1990 and 1999

4. Earth’s surface temperature, 140 yr IPCC 2000

5. Earth’s surface temperature, 1000 yr IPCC 2000

6. Global changes in atmosphere • CO2 content has increased by 31% since 1750 • Higher concentration now than at any time in last 420,000 yr, and probably more than at any time in last 20 million yr • Rate of increase in concentration is unprecedented in the last 20,000 yr

7. Greenhouse gasses IPCC 2000

8. Future changes • Global surface temperature increase by 1.4 to 5.8C between 1990 and 2000 • Land areas will warm more than the oceans, especially northern North America • Larger and faster changes than at any time in last 10,000 yr

9. Future climate extremes IPCC 2000

10. Climate change and fires • What are the implications for fires and their ecological effects? • The answer depends in part on the role of climate vs topography or local fuel conditions in determining fire patterns • We’ll also look at some of the tools people are using to answer these questions

11. Example hypotheses • There are linkages among fire-climate-vegetation-land use-topography across temporal and spatial scales • Regional climate entrains fire patterns at fine spatial scales, overriding the influence of local topography and vegetation, leading to synchrony at widely separated sites and across regions • Fires will mediate the effects of climate change

12. Approaches • Cross-regional studies • Comparative case studies: thoughtful comparisons across time and space, and in different climates will be informative of general theory • Simulation models • Long-term climate-fire-vegetation reconstructions • Combined approaches

14. Drought Swetnam, TW

15. Fire along environmental gradients Swetnam, TW

16. Fire frequency • Fires of some size every few yrs • Larger fires once or twice per decade • Regional fire yrs 2 to 5 times per century • Synchrony • Variable • Factors controlling fire regimes varied through time • Climate important in controlling landscape conditions and ignitions • Wet conditions favored increased fuel production and accumulation • Dry conditions favored effective ignition and spread. • Cool/moist decreased fire frequency, but increased fire size and intensity. • Long-term warm/dry conditions: more frequent fires, but less spatial continuity of fuels and, consequently smaller fires.

17. Implications for the future • Fire regimes will continue to change in response to changing forest conditions and climate • A warmer climate with more frequent burning could change species composition • Wet, warm climate could increase fuel production, with corresponding increases in fire intensity and size • Warmer-drier conditions might lead to intense fires followed by a decrease in fire severity as fuel production declined. • The forest-climate-fire system is dynamic

18. Area burned • Selway-Bitterroot Wilderness Area • 474,237 ha burned in 437 fires from 1880 to 1996 • 7 yrs of extensive fire, 72% of all area burned • 1889, 1910, 1919, 1929, 1934, and 1988 • Gila-Aldo Leopold Wilderness Complex • 147,356 ha burned in 232 fires from 1909 to 1993 • 6 yrs of extensive fire, 71% of all area burned • 1909, 1946, 1951, 1985, 1992, 1993

19. 20 k N Rollins/LTRR

20. Area burned during three different eras of fire management

21. Area burned and Palmer Drought Severity Index (PDSI)

22. Fire frequency • Derived from the fire atlases • Fires >50 ha

23. Gila/Aldo Leopold Wilderness Complex Mogollon Baldy - Langstroth Mesa Transect 1904 9 1965 15 5 1968 5 1953 5 1992 5 37 1953 1904 10 1989 1938 1992 1986 - 1997 fires per 100 ha Lightning Ignitions Human Ignitions

24. Lightning, fires, topography and vegetationGALWC,fires/100 ha,1986 - 1997 Lightning ignitions Human ignitions

25. Climate from tree rings Cross-dating is used to identify missing and false rings, and therefore to get accurate dates Old trees give longer records

26. Changing fire patterns

27. Complex interactions • Fires influence global C • Fires release CO2 • Fire-killed vegetation decomposes • Recovering vegetation may absorb less C • Fires will increase under climate change • Canada may experience a 50% increase in annual area burned (Amiro et al. 2001, Flannigan et al. 1998) • The number of lightning fires could increase by 30% (Price and Rind 1994) • Extended fire seasons Canadian Forest Service. 2001. Forest fire: context for the Canadian Forest Service’s science program. 2001. Available [Online]: <http://www.nrcan-rncan.gc.ca/cfs-scf/science/context_fire/index_e.html>. Accessed November 2001.

28. Drivers • Local site productivity • Topography • Climate • Fire exclusion policies • Land use • Exotic plants

29. Climate-vegetation-land use linkages • Climate is a major driver of fire occurrence in all fire regimes, but • Climate and climate variability only partially explains changes in fire regimes through time • Land use has altered fire regimes: grazing (where fine fuels carry fires), roads (limit fire spread), fire suppression, logging, mining, exotics, etc. • Intensive grazing in dry forests (Swetnam and Baisan 1996; Swetnam and Betancourt 1990, 1998) • Fire suppression (Rollins et al. in press) • Less influential where infrequent, stand-replacing fires were the norm • Fire size has not changed in 20th century in chaparral of CA (Keeley et al. 1999)

30. What have we learned • Climate has an overriding importance at both broad and fine scales (Swetnam and Betancourt 1998; Heyerdahl et al. 2001), particularly for extreme events. • Human impacts are ubiquitous as well, but more pronounced in altering fire regimes where fires were historically frequent (Hardy et al. 2001), and where human population density is high and land use is intense (e.g. chaparral in California, Keeley et al. 1999).

31. Challis National Forest, Idaho, Photo from Amy Haak Salmon R. in Idaho, Photo from Amy Haak